LimeSDR Software Defined Radio

https://www.crowdsupply.com/lime-micro/limesdr

Data Sheets - Support
https://github.com/myriadrf/LMS7002M-docs

Rakon Oscillator data sheet
www.rakon.com/products/families/download/file?fid=39.225

Altera Cyclone IV FPGA data sheet
https://www.google.com/search?q=altera+cyclone+iv+datasheet

About the Airspy software defined spectrograph

Many thanks to the following sources:

http://www.rtl-sdr.com/tag/airspy/

http://forums.radioreference.com/software-defined-radio/280617-airspy-sdr-sdr-author-6.html

http://www.kmitocty.cz/?p=1709

March 2015 Airspy Radiouser  article by Mike Richards
http://www.pwpublishing.ltd.uk/radio-user/

https://www.google.com/search?q=airspy+sdr+images
...

About the SDR-IQ software defined radio and spectrograph

Price ?? 400 US dollars ??

Several reviews at:
http://www.eham.net/reviews/detail/6466

Rfspace:
http://www.rfspace.com/RFSPACE/Home.html

Rfspace SDR-IQ :
http://rfspace.com/RFSPACE/SDR-IQ.html

Google search for reviews :
https://www.google.com/search?q=sdr-iq+review

Gnuradio free and open source software supports it:
http://gnuradio.org/redmine/projects/gnuradio/wiki

Osmocomsdr software :
http://sdr.osmocom.org/trac/wiki/GrOsmoSDR

Yahoo Group :
https://groups.yahoo.com/neo/groups/SDR-IQ/info

David Haworth Stargazing Pages, on receivers for radio telescopes :
http://www.stargazing.net/david/radio/receivers.html

Wiki Radioreference on SDR radios
http://wiki.radioreference.com/index.php/Software_Defined_Radios

Higginson-Rollins and Rogers 2014 - Development of a Low Cost Spectrometer

I take note of Higginson-Rollins and Rogers 2014 :

http://adsabs.harvard.edu/abs/2014AAS...22314824H

http://www.haystack.mit.edu/edu/undergrad/srt/pdf%20files/2013_HigginsonRollinsPaper.pdf

Abstract: "Several instruments used for education, outreach and scientific investigations could benefit from a low cost spectrometer. These include the Small Radio Telescope known as the "SRT", a very small radio telescope known as the "VSRT", and an 11 GHz Ozone spectrometer. The SRT is used to observe the Sun and the 21-cm hydrogen line. The SRTs, which until recently were available commercially, are still in operation at many universities and are used for student projects including measuring the Galactic rotation curve of our Galaxy. These instruments, which were initially primarily used to help teach students how to analyze scientific data, are now used for scientific investigations that have resulted in publications in science journals. Recently a low cost USB "dongle" for digital TV has become available. It has been adapted for use as a software defined radio by amateur radio groups. Linux-based software was developed to adapt the device to form a low cost digital spectrometer for the SRT by integrating open source code into the existing C code written for the SRT. Some challenges faced when trying to integrate the USB TV dongle into the SRT system and software will be discussed. To test the effectiveness of the USB TV Dongle based SRT several astronomical observations were made and compared to the older SRT system. These observations show promise for the device replacing older SRT systems at a fraction of the cost and effort and as a possible replacement for the VSRT and Ozone spectrometer."

RTL Meets Radio-SkyPipe and RS Spectrograph -- RTL Bridge

I refer to Jim Sky's post about his "RTL Bridge" software:

http://cygnusa.blogspot.com/2014/07/rtl-meets-radio-skypipe-and-rs.html

http://radiosky.com/spec/RTL_Bridge_Help.html

http://www.rtl-sdr.com/radio-astronomy-rtl-bridge-radio-sky-spectrograph/

"...I have written an application that allows you to use inexpensive RTL dongle radios to feed my strip chart program, Radio-SkyPipe (RSP), and my Radio-Sky Spectrograph (RSS), with wideband data.  The program is called RTL Bridge...I consider this experimental as of now, and invite others to test RTL Bridge with RSS and RSP.  If you think you want to try it read the help file here. You will need to install RSS if you have not done so and if you already have it installed, you will need the new update.  It is all in that help file. RSS is free by the way.  This could be the start of a nice hydrogen line study for very little money."